干湿交替对自然沟渠沉积物反硝化速率的影响

Effect of wet and dry alternation on denitrification in natural ditch sediments

以川中丘陵区自然沟渠沉积物为研究对象,设置低强度、中强度、高强度的干湿交替频率和长期淹水对照处理,运用室内原状土柱⁃乙炔抑制培养法和实时荧光定量PCR技术,研究了干湿交替对自然沟渠沉积物反硝化速率及相关功能基因的影响.结果表明:在试验模拟过程中,干湿交替显著降低了沉积物中NH+4⁃N和DOC含量,沉积物中NO-3⁃N含量则表现为先增加后减少的趋势.沉积物反硝化速率均值表现为中强度(266.42μg·m-2·h-1)>高强度(199.10μg·m-2·h-1)>低强度(152.93μg·m-2·h-1)>长期淹水(9.57μg·m-2·h-1).干湿交替增加了反硝化功能基因的拷贝数(p<0.05),nosZ基因拷贝数在实验前后无显著差异;低强度和中强度处理的nirK基因拷贝数在实验前后差异显著,中强度处理的nirS基因拷贝数在实验前后差异显著.Pearson相关分析结果表明,沉积物的反硝化速率与NO-3⁃N含量、ORP和nirK基因拷贝数呈显著正相关(p<0.05).干湿交替可能主要通过改变沉积物的NO-3⁃N含量、ORP和nirK基因拷贝数影响沉积物反硝化速率.

The effect of alternating dry and wet conditions on the denitrification rate and related functional genes in natural trench sediments were investigated by conducting three experimental treatments of the low⁃intensity,medium⁃intensity,high⁃intensity dry⁃wet alternating frequency and the control of long⁃term flooding control with indoor undisturbed soil column⁃acetylene suppression culture method and real⁃time PCR technology.The results showed that the alternation of wet and dry significantly decreased the contents of NH+4⁃N and DOC in the sediment,and the contents of NO-3⁃N in the sediment with a trend of increasing first and then decreasing during the experiment simulation.The mean value of sediment denitrification rates for different wet and dry alternation have the following pattern,i.e.medium intensity(266.42μg·m-2·h-1)>high intensity(199.10μg·m-2·h-1)>low intensity(152.93μg·m-2·h-1)>Long-term flooding(9.57μg·m-2·h-1).Alternating dry and wet increased the copy number of the denitrification function gene(p<0.05),but no differences in nosZ gene between before and after the experiment;the significant difference in nirK gene between before and after the experiment of treatment were low⁃intensity and medium⁃intensity;the significant difference in nirS gene between before and after the experiment of treatment was medium⁃intensity.Pearson correlation analysis results showed that the denitrification rates of sediments were positively correlated with NO-3⁃N content,ORP and nirK(p<0.05).Dry⁃wet alternation could affect the denitrification rate of sediment mainly through regulating the NO-3⁃N content of the sediment,ORP and nirK gene copy number.